>
seen
BA
:
a“
.
8a
‘
ate
.
.
ee
a
EAE lean
nee
26
The variation in the ratiog Co°7/zn65 and Co?!/fe2> in
plankton samples with change in collection site may also be
due to differences in levels of the three tsotopes in the
fallout material.
However,
the possibilities should not be
overlooked that it may be due to preferential scavenging of
zine by calcite and calcium hydroxide in the area of intense
fallout or to blological effects.
Data that would resolve
these points are not Evallable and an effort should be made
to obtain the necessary information in any future operation.
Evidence that the differences in Co57/zn®©5 ratios are
real and not due to techniques of separation and analysis
is found in the gamma spectrum curves on whole plankton
samples (Fig. 2).
Inspection of the curves from the three
samples shows clearly the differences between the levels of
zn©5 and both of the cobalt isotopes, Co57 and Co®9, in the
whole sample before separations and analyses were performed.
ae Se
ae